1. Field of the Invention
The present invention relates to a parts handling apparatus, and more particularly, to a structure of an apparatus best-suited to handle electronic parts in an electrical characteristic inspection of integrated circuit (IC) devices.
2. Description of the Related Art
In a conventional process of inspecting the characteristics of integrated circuits (ICs), an IC handler is used to sequentially place many IC devices in an inspection position and to inspect the IC devices. The IC handler is provided with a contact hand for holding the IC device by suction. The contact hand repeats operations of carrying an IC device from a parts supply position, supplying the IC device to an inspection socket located in the inspection position, taking the IC device out of the inspection socket at the completion of an electric characteristic inspection on the IC device, and carrying the IC device to a parts discharge position.
In the characteristic inspection process using the IC handler, it is required to make an inspection on many IC devices in a short time. Here, the time, which is used to take an inspected IC device out of the inspection socket, to set the next IC device to be inspected on the inspection socket and to put outer terminals of the IC device into a stable contact with the inspection socket, is called "index time". In the above process, it is most important to shorten the index time, and the performance of the IC handler is evaluated by the length of the index time thereof.
One of the most effective methods for shortening the index time is to provide a plurality of contact hands, usually two contact hands, for accessing one inspection position. The provision of two contact hands makes it possible that one contact hand takes an inspected IC device out of the inspection socket and the other contact hand immediately sets an uninspected IC device on the inspection socket. Therefore, the index time of the IC handler can be shortened.
FIG. 9 shows the schematic structure of an IC handler which shortens the index time as mentioned above. In this IC handler, two inspection sockets 11 are placed in an inspection position, and a parts discharge stage 33 for receiving two IC devices from the inspection sockets 11 and a parts supply stage 34 for supplying two IC devices to the inspection sockets 11 are fixed on a shuttle 35 located on one side of the inspection sockets 11 and 11. The shuttle 35 is so structured as to reciprocate in the extending direction thereof and to put the parts discharge stage 33 and the parts supply stage 34 into a predetermined supply and discharge position (IC device handling position) alternately.
Two turning arms 31, spaced at 180.degree. about a turning shaft O, are interposed between the inspection sockets 11 and the shuttle 35. The two turning arms 31 turn about the vertical shaft O integrally on a horizontal plane. Each of the turning arms 31 is provided with a transfer mechanism 32 fixed at the leading end thereof, and a contact hand 5 is mounted at the bottom end of the transfer mechanism 32 to be movable upward and downward. The contact hand 5 can grasp two IC devices arranged on the parts supply stage 34 at a time, and place the IC devices on the inspection sockets while grasping. When one transfer mechanism 32 at the leading end of the turning arm 31 is placed just above the inspection position, the other transfer mechanism 32 is placed just above the handling position on the shuttle 35. The two transfer mechanisms 32 transfer IC devices from the parts supply stage 34 to the inspection sockets 11, and from the inspection sockets 11 to the parts discharge stage 33, alternately.
In the state shown in FIG. 9, unillustrated IC devices are held by the contact hand 5 placed just above the inspection sockets 11, and set on the inspection sockets 11 by moving the contact hand 5 downward. On the other hand, inspected IC devices are held by the contact hand 5 placed above the shuttle 35, and put onto the parts discharge stage 33 in the handling position on the shuttle 35 by moving the contact hand 5 downward.
Next, after the parts supply stage 34 is put into the handling position by moving the shuttle 35, the contact hand 5 moves down, takes uninspected IC devices from the parts supply stage 34, and moves up again. When the characteristic inspection on the IC devices set on the inspection sockets 11 is completed, the contact hand 5 grasping the inspected IC devices moves upward.
The two turning arms 31 turn through 180.degree. in this state, and thereby, the contact hand 5 grasping the uninspected IC devices is moved above the inspection sockets 11 and the contact hand 5 grasping the inspected IC devices is moved above the handling position on the shuttle 35. At this time, the empty parts discharge stage 33 is placed in the handling position on the shuttle 35.
In this IC handler, since the IC devices are supplied and discharged alternately by the two contact hands 5 while turning the turning arms 31 through 180.degree., the index time equals to the sum of the time taken for one contact hand 5 to take IC devices from the inspection sockets 11, and the turning time of the turning arms 31 and the time taken for the other contact hand 5 to set IC devices.
However, since the IC devices are conveyed from the handling position to the inspection position by turning the turning arms 31 in the above-mentioned IC handler, the conveyance trail of the IC devices is shaped like an arc, and the conveyance distance is p/2 times as long as that of the linear movement. Therefore, in order to obtain an index time equivalent to that of the linear movement of the IC devices, the conveyance speed and acceleration required to convey the IC devices are both increased, which needs a higher-powered drive source and a more rigid conveying mechanism. Particularly, in order to turn the transfer mechanism 32 and the contact hand 5, which are provided with heavy components such as a driving cylinder and a motor, more swiftly, high driving power is needed to increase the acceleration and deceleration. Therefore, it is quite difficult to achieve such swiftness while keeping the precision of the conveyance position and the structural precision.
As another method for further shortening the index time, it is thought of to increase the number of turning arms as shown in FIG. 10. In the structure shown in FIG. 10, three turning arms 36 are located about a turning shaft. Since the turning arms 36 are spaced at 120.degree., it seems that the moving distance of IC devices is decreased and thereby the index time is shortened. However, this case requires each of the three turning arms 36 to be provided with a transfer device 32 and a contact hand 5 at the leading end thereof, which increases the number of components of the apparatus and the weight of the moving parts, and needs higher driving power. Therefore, it is difficult to increase the operation speed of individual moving parts, and the manufacturing cost of the IC handler increases.
Furthermore, in the IC handler shown in FIG. 10, it can be thought of that the inspection ability is enhanced without shortening the index time by increasing the number of IC devices to be grasped by each contact hand 5 and the number of IC devices to be inspected by the inspection socket 11 at a time. However, in this method, the manufacturing cost of the contact hand 5 and the socket 11 increases according to the increased number of IC devices, and the turning radius is required to be increased by making the turning arms 36 longer in order to prevent the interference among the contact hands 5 resulting from the increased length thereof in the turning direction. As a result, the moving distance of the IC devices is increased, and thereby the index time is increased on the contrary.